1. Field of the Invention
The present invention relates to a method and a device for displaying an image on an array screen by activation of screen pixels arranged in rows and columns.
2. Discussion of the Related Art
The present invention especially applies to array screens in which each pixel is formed of a light-emitting diode, for example, of organic or polymer nature (OLED-type screen, for Organic Light-Emitting Display, or PLED, for Polymer Light-Emitting Display). The cathodes of the diodes of a same line are connected to a row electrode and the anodes of the diodes of a same column are connected to a column electrode.
The display of an image on screen, according to usual standards, is obtained by the display of a frame or of two successive frames. Upon display of a frame, the addressing of an array screen is performed row after row via a row control circuit (commonly called the row driver). In the case of an array screen with diodes, the row electrode of the active row may be grounded while the other row electrodes may be left at high impedance or be connected to a high voltage. Simultaneously, the information corresponding to the activation or to the non-activation of the row pixels will be transmitted by the column electrodes via a column control circuit (column driver) which injects or does not inject a current into each electrode column to turn on or to not turn on the column pixel.
It is possible for no pixel of one or several rows to be on upon display of several successive frames, for example, in some applications for portable phone screens or electronic diary screens. Now, such lines will be however activated upon successive addressing of all the screen lines. The power necessary for the row driver to address lines where no pixel is turned on is then uselessly wasted.
Further, in the case of an array screen with light-emitting diodes, upon activation of a row, there often is a previous step of precharge of all the diodes of the row to a voltage close to the threshold voltage. The possible turning-on of the diodes can then be obtained more rapidly. In the base where no pixel in the row is to be activated, the power required for the precharge step is uselessly wasted.